The present invention relates to a measurement method of a polarization characteristic, an exposure apparatus, and a device manufacturing method.
A projection exposure apparatus has been conventionally used to manufacture fine semiconductor devices with the photolithography technology. The projection exposure apparatus transfers a pattern of a reticle or mask to a substrate, such as a wafer, via a projection optical system. Since this exposure apparatus is required to precisely transfer a reticle pattern to a substrate at a predetermined magnification, it is important to use a projection optical system having a good imaging characteristic. In addition, a polarization illumination is also used to improve the imaging characteristic. Consequently, a precise measurement of the polarization characteristic of the projection optical system, such as a birefringence amount, a fast axis, and a Jones matrix, is increasingly demanded. In addition, a simplified measurement is important to enhance the productivity and the economic efficiency.
The birefringence is usually calculated by measuring a phase difference after the light transmits through a sample with a predetermined thickness, and normalizing it with the sample's thickness. This amount is referred to as a “birefringence amount” or “retardance.” In addition to the retardance, it is also important to obtain a fast axis and Jones matrix of the projection optical system.
The Senarmont method, which is a typical measurement method of the retardance, determines the ellipticity and ellipse's major axis, and calculates the retardance through an elliptical polarization analysis by combining a ¼ retardation sheet with a polarizer, and converting the elliptically polarized light that has transmitted through the sample back to the linearly polarized light. A method that calculates the retardance from the light intensity, such as a rotational analyzer (polarizer) and a phaser method, also utilizes a ¼ retardation sheet and a polarizer. The optical heterodyne interferometry uses a ½ retardation sheet and a polarizer to calculate the retardance.
Prior art include, for example, Japanese Patent Applications, Publication Nos. 2004-61515 and 11-054411, and Yasuyuki Unno “Influence Of Birefringence On The Image Formation Of High-Resolution Projection Optics,” 1 Jul. 2000, Vol. 39, No. 19, APPLIED OPTICS (simply referred to as “Unno” hereinafter).
Thus, the prior art use such optical elements as the ½ or ¼ retardation sheet, polarizer, and analyzer to measure the retardance in the polarization analysis. Thus, an incorporation of these optical elements into an originally complicated system would increase the cost and design load.